1. Field of the Invention
The present invention relates to a silica film forming material suitable for a multilayer wiring structure in a semiconductor integrated circuit, a silica film formed by using the silica film forming material and a method of manufacturing the same, a multilayer wiring structure and a method of manufacturing the same, and a semiconductor device comprising the silica film as an interlayer insulation film or a protection film and a method of manufacturing the same.
2. Description of the Related Art
With the increase in the level of integration of semiconductor integrated circuits and the improvement of element density in recent years, the demand for higher lamination semiconductor integrated circuits is especially rising. With the trend for higher integrated semiconductor circuits, the space between wirings is becoming narrower, which is creating the problem of a wiring delay due to an increase in inter-wiring capacity. Here, the wiring delay (T) is expressed as the following formula: T∝CR, and is affected by the wiring resistance (R) and the inter-wiring capacity (C). Furthermore, the relationship between the dielectric constant (∈) and the inter-wiring capacity (C) is expressed with the following equation: C=∈0∈r·S/d, where S is an electrode area, ∈0 is a electric constant, ∈r is a dielectric constant of the insulation film, and d is a space between the wirings, respectively. The inter-wiring capacity (C) may be decreased by making the wiring thickness to be thinner to reduce the electrode area, but making the wiring thickness thinner causes a further rise in the wiring resistance (T), which in turn prevents the achievement of higher speed. Hence, lowering the dielectric constant of the insulation film becomes an effective method for minimizing the wiring delay (T) and achieving higher speed.
With an increase in the level of the integration of the semiconductor integrated circuit and the improvement in element density in recent years, a space between metal wirings tends to become narrow in a semiconductor device having a multilayer wiring structure. Hence, the impedance of the metal wiring due to static electricity induction is rising, leading to concern that the response speed may be delayed and electric consumption is growing. For this reason, it becomes crucial to make the relative dielectric constant of the interlayer insulation film provided between the semiconductor substrate and the metal wiring layer or between the metal wiring layers to be as small as possible.
Example of conventional material of the insulation film is an inorganic material such as a silicon dioxide (SiO2), a silicon nitride (SiN), and a phospho-silicate glass (PSG), or an organic polymer material such as a polyimide. However, the dielectric constant of CVD-SiO2 film frequently used in semiconductor device is high at around 4. Moreover, SiOF film, which is considered to be used as low dielectric constant CVD film, has a dielectric constant of about 3.3 to 3.5, but it has the problem of high moisture absorption properties that result in a rising dielectric constant over time. Moreover, porous silica film having low dielectric constant has been proposed (See Japanese Patent Application Laid-Open UP-A) No. 2004-153147). The method of manufacturing such a porous film enables further lowering of the dielectric constant because the method contains a process in which the heat-degradable components are heated and degraded to form pores.
However, in the case of porous film of the siloxane resin, etching processing is difficult due to the properties of such a porous film, hence formation of plasma CVD film such as SiCH with a dielectric constant of about 4.5 in order to protect the film is required. This presents a problem in which the low dielectric constant properties of the porous film cannot be utilized effectively. Moreover, in forming fine wirings of 0.1 μm or less, an insulation film hard mask, a three-layered resist or the like is applied, which presents a problem in which the short of wirings or the leak current through the insulation film is created due to the impossibility of a high-degree of etching selectivity relative to the porous film or protective film in a dry etching.
An objective of the present invention is to overcome the aforementioned problems of the related art, and to achieve the following object. In fact, an object of the present invention is to provide: a silica film which excels in properties of etching resistance, chemical resistance, and moisture resistance with superior adhesive properties and has a low dielectric constant; a method of effectively forming the silica film; a silica film forming material suitable for forming the silica film; a multilayer wiring structure enabling lowering of the parasitic inter-wiring capacity; a method of effectively forming the multilayer wiring structure; a semiconductor device with high reliability and high speed having the silica film as an interlayer insulation film or protection film; and a method of effectively manufacturing the semiconductor device.